The Subscriber Identity Model (“SIM”) used in mobile communication technologies is applied widely as a client identification device of mobile communication terminals. With the development of technologies and science, various intelligent circuit modules are added into the SIM card of an ordinary mobile communication terminal via different kinds of ways to make the SIM card have functionalities closer to the daily life in addition to basic SIM card functionalities. A Radio-Frequency (“RF”) SIM card is one of the examples. China Patent No. 200710124354.7 discloses corresponding technologies.
An RF IC card device with high frequencies described in China Patent No. 200710124354.7 adopts active RF technology, which can have mobile payment functions such as E-wallet or consumer application functions such as mobile-phone access pass. But for certain payment application functions, for transaction safety, a wireless communication distance must be controlled within a very small range, such as within a bus or metro, to avoid unconscious long-distance mis-transactions. So communication distance control becomes the most difficult goal to achieve.
The short distance card-swiping mechanism (i.e. a mechanism of constraining the card-swiping distance) of existing RF SIM cards determines the distance through checking parameters of RF power intensity. But this mechanism does not take into account an impact of a temperature (under same emission power, the lower a temperature is, the higher a field intensity value is detected) on RF emission power and detection. Thus, changes to external ambient temperature will affect the accuracy of the distance determination.